This invention relates to a crimped continuous filament yarn having enhanced bulk level, and for a process of making such yarn. More particularly, the invention relates to a process at high speed giving excellent crimp uniformity and regularity.
Numerous types of yarns and processes having crimp and bulk have been proposed in the prior art, and are particularly useful when the yarn is to have substantial stretch. Typical conventional texturing machines known in the trade apply the method of false twisting by a rotating spindle as shown in U.S. Pat. Nos. 3,738,095 and 3,740,939. The disadvantages of the methods of these patents is that the process involves relatively slow speeds (maximum of 400 meters/minute), and the process is lubricant sensitive. In addition, spindles have to be cleaned periodically from yarn finish deposits to remain operational. Another known system of texturing is false twisting in a fluid jet as shown in Bense U.S. Pat. No. 3,742,692, which tends to give low bulk levels.
Another type of crimped yarn is produced by conjugate spinning, i.e. extruding two polymer components in a parallel relationship into a single filament. If the polymer components have different shrinkages, the drawn filament will develop crimp when heated. Conjugate spinning has a number of disadvantages, such as the necessity for metering the two components to the spinneret orifices, and the elaborate distribution passageways required for properly distributing both polymer components to each orifice. (Breen U.S. Pat. No. 2,931,091)
Another crimped yarn is produced by drawing a homogeneous or single component yarn over a sharp edge. In this process a helical crimp is produced, which tends to be irregular. A further prior art process is disclosed in U.S. Pat. No. 3,226,792 to Starkie, wherein nylon 66 yarn is stretched, heated on one side to a temperature below the melting point of the yarn, while being cooled on the opposite side. This yarn is later unwound, placed in hot water to develop, crimp, and rewound.
Another prior art process is disclosed in U.S. Pat. No. 3,769,669, where one side of a monofilament is heated under tension to slightly above its melting point by means of a roll, while the opposite side is kept cool by another roll to below 100.degree.C. This process has not been demonstrated to be usable above a speed of 1,800 feet per minute (550 meters per minute).